The present invention relates to a winding machine for wrapping a multiplicity of coils of rolled material around the same reel and, more specifically, for wrapping at least two coils of rolled material around the same reel. The present invention also relates to an assembly comprising a rolling mill plant managing a multiplicity of strands and connected to such a winding machine.
When rolling small bar diameters, the hourly tonnage rate of the mill is limited by the maximum output speed of the last rolling stand, as the material flow rate is the product of the small bar cross section by the mill rolling speed.
In an attempt to optimize a single strand rolling process, known rolling mills have been arranged to consecutively serve a multiplicity of spooling stations. However, they serve in a way that only one spooling station at a time can be served, for instance thanks to a switching device placed between the rolling mill and the different spooling stations. In this configuration, for example, one first billet is rolled and one corresponding first coil is formed at one first spooling station. Then the switch is diverted to a subsequent, different second spooling station and a following second billet is rolled forming a coil at such second spooling station. Meanwhile the first coil which had been formed in the first spooling station is removed to ready the first spooling station for another cycle. However, the need for at least two spooling stations which, in turn, operate only alternatively, rather than simultaneously each time that a cycle has been completed, does not make this configuration efficient with respect to hourly production rate and to space required, because in the face of a single strand process, two spooling stations are still required.
State of the art rolling plants try to overcome such a limitation of the maximum output speed by rolling the smaller bar diameter in multiple strands in parallel. By concretely doubling, tripling or quadrupling the effective cross section by managing respectively two, three or four strands, and while keeping the maximum output speed as imposed by the last rolling stand, the overall plant output can be proportionally doubled, tripled or quadrupled.
However, several problems arise when a rolling mill has to manage multiple strands in parallel. The main drawback of such configuration is that, when switching from single strand rolling to multiple strand rolling, the equipment downstream of the rolling mill must be adapted to effectively manage a multiplicity of strands in an ordered manner. For instance, when rolling in a slit-mode, a single bar is divided into two bars at a certain moment of the rolling process. The resulting two strands of rolled material can then be rolled in parallel, wherein each strand is strand is guided separately by dry-through conveying channels to a respective spooling station directed by a switching device placed between the rolling mill and the different spooling stations.
At any rate, by rolling in a slit-mode and managing multiple strands in parallel using current technology, even if the hourly production rate is improved, a relatively high number of spooling stations is still needed. Although the slitting technology brings benefits in terms of productivity, the need of additional equipment results in higher spaces required for milling and winding plants.
In general, the number of spooling stations typically required can be up to two times the number of rolled strands, e.g. four spooling stations for two-strand rolling; six spooling stations for three-strand rolling, etc. . . . .
Furthermore, the dry-through conveying channels guiding each of the strands to a respective spooling station are usually made of cast-iron and are therefore considerably heavy and bulky. Ideally, the dry-through conveying channels comprise gentle bends so that the strands can be smoothly guided through the successive rolling stages, thus preventing the strands from being deformed in undesired manner corresponding to the sharp turns. Such a design constraint in the layout of rolling and winding plants evidently implies that a relatively large space is needed for arranging the dry-through conveying channels. A higher number of spooling stations results therefore in a larger area to be dedicated to such dry-though conveying channels.
Consequently, resetting a milling line according to design requirements which are compliant with current slit-mode rolling technology by using the current solutions is still a trade-off between real benefit and return of investment.
Thus, a need exists in the prior art for a winding technology which allows use of a reduced number of spooling stations, both in the case of a substantially single strand rolling process, when a multiplicity of spooling stations are served in succession, each one at a time; and in the case of a multiple strand rolling process, when multiple strands are managed in parallel.